1. Field of the Invention
The present invention relates generally to an optical module, and more particularly, to a dual-port broadband light source.
2. Description of the Related Art
A light source in a broad wavelength band is needed to measure the optical properties of optical devices in the field of optical communications. Especially in the case when an Erbium-Doped Fiber Amplifier (EDFA ) is used in an optical communication system, optical signals may range from 1520 nm to 1620 nm. Thus, a light source is needed that can measure the optical properties of optical devices in the desired wavelength band. A broadband light source used in conjunction with a wavelength locked LD (Laser Diode) is attracting interest as a light source for simultaneously accommodating multiple users in a WDM-PON (Wavelength Division Multiplexing-Passive Optical Network) as a future ultra high-speed optical subscriber network. Existing broadband light sources use ASE (Amplified Spontaneous Emission) light from a white light source or an EDFA. The white light source has limitations in serving as a WDM-PON light source requiring high power or in measuring optical device properties because its output power is weak. The use of an EDFA as a light source, on the other hand, is not cost-effective.
U.S. Pat. No. 6,507,429 entitled “Article Comprising a High Power/Broad Spectrum Superfluorescent Fiber Radiation Source” discloses a broadband light source for emitting a C-band (1520 to 1570 nm) and L-band (1570 to 1620 nm) ASE light. The broadband light source includes first and second rare earth-doped optical fibers and an isolator interposed between them. A first pumping light from a first pump light source is provided to the first rare earth-doped optical fiber and a second pumping light from a second pump light source is provided to the second rare earth-doped optical fiber. A reflector reflects the ASE light emitted from the first rare earth-doped optical fiber back to the first rare earth-doped optical fiber, thereby helping the first rare earth-doped optical fiber generate an L-band ASE light. The second rare earth-doped optical fiber operates to amplify the L-band ASE light and generate a C-band ASE light. Consequently, the broadband light source can output a C-band and an L-band ASE light through its output port.
However, in the typical broadband light source described, the C-band ASE light emitted backward from the second rare earth-doped optical fiber is not utilized because of the isolator between the first and second rare earth-doped optical fibers. Therefore, the broadband light source has low output efficiency. In addition, when the output of the first pump light source is changed to control the L-band ASE light power, the C-band ASE power is also changed. Similarly, if the output of the second pump light source is changed to control the C-band ASE power from the first rare earth-doped optical fiber, the L-band ASE power is also changed. Thus, because the power of the C-band ASE light is closely related to the power of the L-band ASE light, it is not easy to control the output of the broadband light source.